The Serious Fraud Office today officially kicked off an investigation into the New Zealand activities of US-based Brockstar Group, almost a month after the firm first popped up on its radar.

The funds provider, run by Californian businessman Brian Willis, is accused of charging high upfront fees on loans that were never delivered.

Brockstar's alleged fraud was reveal during the trial of Jacqui Bradley, whose B'On ponzi scheme wiped out $14.4 million of clients funds, and from an ongoing investigation into Derivatek.

Both firms are said to have applied for loan packages of $20m, which had upfront fees of $1.3m attached to them.

The fees were paid using client money, but the loans funds were never received.

Bradley, in her failed defence, claimed she intended to use the loan to repay clients, and it's believed the high Brockstar fees accelerated the demise of the financial services firm which she ran with her now deceased husband Michael Bradley.

She was last month sentenced to seven years and five months in prison after being found guilty of 71 counts of fraud.

Business Day has previously reported that Willis has been subject to numerous complaints by investors, and last month the Orange County Superior Court awarded an investor US$837,000 ($1 million) in damages, calling Brockstar's loan business a "classic con game".

Ellis is appealing the judgement, saying the failure to pay the loans or return the fees was due to third parties and the global financial crisis.

Acting SFO chief executive Simon McArley said there is "reason to suspect that an investigation may disclose serious or complex fraud" and is calling on other potential victims to come forward.